1. Field of the Invention
The present invention relates to an apparatus for measuring and evaluating blood flow in a superficial blood vessel using high-frequency ultrasound waves.
2. Description of the Related Art
Recently, lifestyle-related diseases including hyperlipidemia, high blood pressure, diabetes, and visceral fat obesity have become issues, and there is an increasing need for early detection or prevention of these lifestyle-related diseases.
There is an ultrasonic B-mode imaging technique for evaluating a degree of blood cell aggregation which is a potential risk factor of incidence or progression of arterial sclerosis, or thrombus formation (for example, see Japanese Patent Application Laid-Open No. 2005-110724). There is also a study on the simulation for frequency dependence of ultrasonic back scattering on a difference in degree of red blood cell aggregation (for example, see David Savery and Guy Cloutier, “A point process approach to assess the frequency dependence of ultrasound back scattering by aggregating red blood cells”, J. Acoust. Soc. Am. 110(6), 2001).
In the method disclosed in Japanese Patent Application Laid-Open No. 2005-110724, a dynamic property of the blood cannot be evaluated. Although an apparatus to measure the dynamic property of the red blood cells in vitro exists, its measurement results do not indicate blood flow kinetics in the living body. That is, currently the method for invasively measuring and evaluating the dynamic property of the blood flow in human beings in vivo is not established.
In David Savery and Guy Cloutier, “A point process approach to assess the frequency dependence of ultrasound back scattering by aggregating red blood cells”, J. Acoust. Soc. Am. 110(6), 2001, the coagulation time of a pig's blood sample is assumed to represent a red blood cell aggregation rate, and the degree of back scattering in high frequencies of 12.5 MHz or more is estimated by simulation based on experimental data in relatively low frequencies of 3.5 MHz to 12.5 MHz.
Human skin is acoustically different and varies from individual to individual, therefore it is difficult to measure the blood flow in human skin under the same condition without the influence of individual differences.
An object of the invention is to provide means for measuring and evaluating the dynamic property of the blood flow in the superficial blood vessels of human beings in vivo. Another object of the invention is to provide a method for measuring the ultrasound wave under the same condition irrespective of the influence of individual differences.